Here's a couple of pics of my second frame that I finally finished earlier this year, though its now sporting a rather bright 'tonka truck' yellow paint job:

You can get away with quite simple jigs and a bit of imagination and alot of patience (heres what I built my first frame on):

The DIRT mag website has done a few features on homemade bikes (my mk1 included) which are worth checking out if your interested in homebrews, and show a range of designs/constructions and approaches: http://dirt.mpora.com/tag/homemade-bikes